Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only mark the operation as not read-only, open-world, and non-destructive; the description adds useful context (server-signed, Ed25519, five-minute validity) but does not disclose side effects, rate limits, or what happens to previous challenges. It does not contradict annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

One tightly scoped sentence front-loads the action and resource, then adds the target condition. Every phrase contributes and nothing is redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The definition is adequate for a basic call because the input schema documents the complex nested object, but there is no output schema and the description does not explain the challenge response structure, encoding, or how the challenge is used with complete_participant_registration. For a high-complexity registration flow, this is a noticeable gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0% at the top level, so the description must compensate for parameter meaning. It only refers to a 'schema-valid agent.external registration' without naming registrationRequest or explaining how the nested required fields relate to the returned challenge; the schema must do all the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb and resource: 'Request a five-minute server-signed Ed25519 challenge.' It further scopes the target to 'schema-valid agent.external registration,' which makes the operation distinct from sibling tools like complete_participant_registration and get_participant_registration_requirements.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies the tool is used during agent external registration ('for any schema-valid agent.external registration') and in a 'cryptographic challenge-response' flow, but it never states when to use it relative to complete_participant_registration, nor does it name alternatives or prerequisites.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.